Polymerization process



United States Patent 3,418,292 POLYMERIZATION PROCESS Irving E. Muskat,Miami, Fla., assignor, by mesne assignments, to Sinclair Research, Inc.,a corporation of Delaware No Drawing. Continuation of application Ser.No.

191,276, Apr. 30, 1962. This application Jan. 3,

1967, Ser. No. 607,076

11 Claims. (Cl. 26078.5)

ABSTRACT OF THE DISCLOSURE There is disclosed an improved method ofcopolymerizing an olefinic compound, e.g., styrene, and a maleiccompound, e.g., maleic anhydride, which involves simultaneously bringingthe olefinic compound, the maleic compound and a free-radical initiatingcatalyst, e.g., a peroxide catalyst such as benzoyl peroxide, intocontact with a solvent which has been pre-heated to the desiredpolymerization temperature, e.g., about 75 to 300 C., and in which boththe reactant monomers and the copolymer product are soluble.

This application is a continuation of application Ser. No. 191,276,filed Apr. 30, 1962, now abandoned.

The present invention is concerned with a novel method ofpolymerization, especially the copolymerization of an olefinic compoundsuch as styrene, with a maleic compound such as maleic anhydride.

The copolymerization of certain olefinic compounds With certain maleiccompounds has long been known and various techniques of solution, bulk,and the like processing have been described. One of the most importantcopolymerization processes has been the copolymerization of styrene withmaleic anhydride to form a copolymer in essentially a 1:1 molar ratio.This copolymerization has been performed in a bulk type reaction; e.g.,wherein the reagents along with the catalyst, usually a peroxidecatalyst, are mixed together and then heated to polymerizationtemperature. In those instances wherein an organic liquid media, usuallybenzene or xylene, is employed, the reagents are again generally mixedinto the media and the entire mixture then heated to the appropriatereaction temperature. Two classes of liquid media have been employed;viz., those in which the copolymer product is insolublefor example, thehydrocarbons such as xylene; and those in which the copolymer product isessentially completely soluble, resulting in a homogeneous solution. Inthe latter instance, certain ketones such as acetone and methyl ethylketone have been employed. The abovedescribed processing is set forth inmore detail and typified by U.S. Patents Nos. Reissue 23,514, 2,313,728,2,430,313, 2,640,819, and 2,675,370.

Despite the wealth of work done in this area, there still exist certainprofound and inherent disadvantages to the prior art processes. By Wayof example, the prior procedures have suffered from the inherentdisadvantage that the polymerization reaction is uncontrollable once ithas been initiated. Indeed, proceduresespecially in relation to thecopolymerization of styrene with maleic anhydridehave resulted inserious explosions, thus preventing the most effective utilization ofthe copolymer materials by the industry. A still further inherentdisadvantage of the prior art process has been that only high molecularweight, high viscosity copolymers having only a 1:1 molar ratio ofstyrene to maleic anhydride have been heretofore obtainable. A stillfurther inherent disadvantage of the prior art procedures is that thecopolymers produced generally have a broad molecular weight range andthus the utility of the copolymers is adversely affected.

Patented Dec. 24, 1968 The copolymers of olefinic compounds such asstyrene with maleic compounds such as maleic anhydride are ofconsiderable utility, particularly for employment as resins orderivatives thereof in paints, floor polishes, textile sizing, tanningsolutions and the like. Therefore it is highly desirable to the industryto provide a more effective and efiicient mode of producing suchcopolymers which would thereby not only increase the aforementioned usesthereof, but also promote even additional uses by virtue of theirgreater availability and the even more consistent and specificproperties of the products obtained.

Accordingly, an object of the present invention is to provide a moreeffective and improved method for the copolymerization of an olefiniccompound with a maleic compound. A further object is to provide aprocess wherein the danger inherent in the prior art processes isobviated. A still further object is to provide a process wherein moreconsistent and specific properties of the copolymer are obtained,especially wherein copolymers of low molecular weight and low viscosityare obtained. A specific object of the invention is to provide animproved process for the copolymerization of styrene with maleicanhydride in varying molar ratios, especially from 1 to 3 moles of theformer per mole of the latter, employing a peroxide catalyst. Otherobjects will be apparent from the discussion hereinafter.

The above and other objects are accomplished by simultaneously bringingan olefinic compound, a maleic compound, and a free-radical initiatingcatalyst together either with or without a solvent and into contact witha solvent which has been pre-heated to the desired polymerizationtemperature, and which is a solvent for both the monomers and thecopolymer produced. A most effective method for proceeding according tothe novel processing comprises first forming a solution of the olefiniccompound, the maleic compound, and the free-radical generating catalystat conditions wherein essentially no copolymerization takes place; thenfeeding this solution to a solvent, preferably the same solvent as thatwhich is employed for forming the solution, which has been preheated andis maintained at the desired polymerization temperature, and whichpreferably contains less than about 3 percent by Weight of unreactedmonomers therein, with the feeding of the solution being at a rate whichdoes not substantially exceed the rate of copolymerization of themonomers, nor exceed the maximum of about 3 percent by weight ofunreacted monomers resulting in the pre-heated solvent. Of the olefiniccompounds, the arylsubstituted a-olefins, especially styrene, arepreferred; and of the maleic compounds, maleic anhydride is preferred.Likewise, for the most effective results, the lower boiling simpleketones, especially those wherein at least one carbon atom attached tothe carbonyl carbon atom contains at least one hydrogen atom bondedthereto, are employed as the solvent. It has also been found that thebest results are obtained when the polymerization reaction is conductedat a temperature between about -250 C.; i.e., the solvent to which thereagents are fed, as set forth above, is maintained at thesetemperatures. Thus, by way of example of a particularly preferredembodiment of the invention, styrene and maleic anhydride inpredetermined molar proportions in conjunction with between about 0.001to 5 percent by Weight of benzoyl peroxide catalyst, based on the totalweight of the monomers, are dissolved in a sufiicient amount of methylethyl ketone to result in a solution containing between about 20-50percent by weight, based upon the total weight of the solution ofmonomers and catalyst, at a temperature which does not result inpolymerization (usually below about 50 C.), and the resulting solutionis then fed to methyl ethyl ketone which has been pre-heated and ismaintained at a temperature between about 75-250 C., with the feeding ofthe solution being at a rate so as not to substantially exceed the rateof copolymerization of the monomers. Other embodiments and more specificdetails of the invention will be evident as the discussion proceeds.

The processing of the present invention as briefly described andsummarized above has many particular advantages over the prior art. Byway of example, a new process is obtained which eliminates the prior artproblem of violent and, in many cases, explosive reaction especiallywhen styrene and maleic anhydride are the reactants. Indeed, in allinstances the reaction proceeds smoothly with safe operation, includingoperation at temperatures higher than heretofore contemplated and withpercent catalyst higher than heretofore contemplated, to produce thedesired copolymer in essentially quantitative yield with extremely fastreaction rates. In nearly all instances, the copolymerization iselfected essentially instantaneously; and with simple, continuousoperation techniques, the rate of production and throughput per unitreactor is enhanced many fold, while additionally avoiding mechanicaldifiiculties with regard to pluggage of lines, recovery of product, andcontrol of reaction conditions. The processing permits the production ofcopolymers, particulraly of styrene and maleic anhydride, of lowermolecular weight and viscosity than made heretofore by the prior artprocedures. Still further, the present invention provides a moreetficient technique for preparing the higher molecular weight and higherviscosity materials previously known to the art..

Still additionally, the process is employable for the production ofcopolymers containing two or more moles olefinic compound, especiallystyrene, per mole of maleic compound, especially maleic anhydride;whereas by the prior art procedures, such copolymers have not beenprepared. By way of further illustration of the advantages of thepresent process is the feature of polymerization occuring only at thedesired temperature avoiding partial pre-polymerization, uncontrolledreaction, and the like. Another advantage which is worthy of particularnote is that the copolymer is obtained dissolved in the solvent and canbe employed for various uses as such; e.g., in coating, impregnating,and molding compositions and the like. Likewise, upon hydrolysis orneutralization of the copolymer, after removal of the solvent, evensignificant quantities of solvent that might be retained in thecopolymer product do not result in murky or cloudy solutions, as areobtained with previously employed diluents such as xylene, benzene, andtoluene. Still other advantages will be apparent from the furtherdiscussion hereinafter.

While the invention is particularly adaptable to the copolymerization ofstyrene with maleic compounds, especially maleic anhydride, it is to beunderstood that olefinic compounds in general are employable. Theolefinic compounds include monoolefinic and polyolefinic compounds, bothconjugated and nonconjugated. Compounds in which the double bond iscontained between two terminal carbon atoms of a carbon chain; i.e.,a-olefins, are particularly suitable because of their greater reactivityin the copolymerization reactions. Thus typical but non limitingexamples of mono-olefinic compounds which are employable include truehydrocarbon olefins such as ethylene, propylene, butene-l, cyclohexen,pentene-l, 4-methylpentene-l, 3-methylhexene-1, 3'methylpentene-l, styrene, vinyl toluene; vinyl halides such as vinyl chloride, bromide oriodide; mono-olefinic esters such as allyl acetate, vinyl acetate, vinylpropionate, and the like; mono olefinic ethers such as vinyl ethylether, vinyl butyl ether and the like; esters of mono-olefinic acidssuch as methyl acrylate, ethyl methacrylate and the like. Included amongtypical but non-limiting polyolefinic compounds are butadiene, isoprene,chloroprene, 4-vinylcyclohexene-1, pentadiene-1,3, diallyl phthalate,and the like. Of such olefinic compounds, those which exhibit anexothermic polymerization reaction with the maleic compound (especiallymaleic anhydride) are preferred. Still further examples of themono-olefinic compounds will now be evident. It

is to be understood that the afore-mentioned compounds can be furthersubstituted with functional groups such as the halogens, keto, nitro andthe like groups, provided such are essentially inert in the system anddo not significantly inhibit the copolymerization reaction- In general,the olefinic compounds are further defined as such which are preferablysoluble in the solvent employed at reaction conditions. The trueolefinic compounds, i.e., such compounds containing only carbon andhydrogen, especially such mono-olefinic compounds, have been found to beparticularly effective. A specially preferred class of mono-olefiniccompounds to be employed comprises the vinyl mono-cyclic aryl compoundshaving only one vinyl group attached to the ring and having not morethan 3 alkyl groups also attached to the ring, wherein the alkyl groupscontain up to and including about 3 carbon atoms. Styrene and vinyltoluene, especially the former, comprise particularly preferred olefiniccompounds because of their greater availability, reactivity, andresulting more beneficial properties inherent in the copolymers producedtherewith.

The maleic compounds copolymerized with the above olefinic compoundsare, in general, compounds which have one carboxyl group attached toeach carbon atom of an olefinic group; i.e., wherein two carbon atomsare joined by a double bond. The remaining valences of each of thedoubly bonded carbon atoms are generally satisfied by organic groupingsor inorganic groupings which are essentially inert in the principalcopolymerization reaction. Thus, the maleic compound will have only oneolefinic linkage. Illustrative of such maleic compounds are materialsdefined by the following structural formula:

wherein R and R can be hydrogen, a halogen, the sulfonic acid radical oran alkyl, aryl or aralkyl radical and X and Y can be OH, O-alkyl, O-arylor a halogen, or X and Y together can be oxygen or NH. Another way fordefining such maleic compounds is to term them asethylenic-a,B-dicarboxylic compounds. Thus, typical examples of themaleic compounds include maleic anhydride, methyl maleic anhydride,propyl maleic anhydride, 1,2-diethyl maleic anhydride, phenyl maleicanhydride, cyclohexyl maleic anhydride, benzyl maleic anhydride, chloromaleic anhydride, and the corresponding derivatives of maleic acid;dimethyl maleate, diethyl maleate, dibutyl maleate, diphenyl maleate,and the like esters; maleic acid chloride, bromide or iodide; fumaricacid and its corresponding substituted derivatives; and the like. Ingeneral, such maleic compounds are further defined as preferably beingsoluble .in the solvent employed at reaction conditions; and,ordinarily, will preferably contain up to and including about 14 carbonatoms. Maleic anhydride is especially preferred because of its greateravailability and the particularly unique copolymers obtained when suchis employed as a comonomer, especially in conjunction with styrene asthe other comonomer. I

As indicated above, a solvent is employed for particularly advantageouspurposes in the instant process, and this solvent is generally definedas one which will dissolve the monomers and catalyst employed, as wellas the copolymer which is produced at the reaction conditions andpreferably also at normal conditions. The solvent is also preferablyessentially inert in the reaction system in the sense that it isnon-reactive with the olefinic or maleic compound. It can, however,exhibit a chain terminating effect and, in some cases, such compoundsare preferable. While any solvent which meets these criteria and is alsoliquid under the reaction conditions can be employed, it has been foundthat the ketones are particularly well suited. Illustrative of suchketones are acetone, diethyl ketone, dipropyl ketone, cyclohexanone,methyl ethyl ketone, ethyl propyl ketone, benzyl phenyl ketone, butylphenyl ketone, and the like. While, in general, such ketones can befurther substituted by functional groups which are essentiallynon-reactive in the system, such as the halogens, nitro, hydrocarbon andthe like groups, it is preferred that the ketone contain only carbon,hydrogen and oxygen atoms. Ketones which contain a carbon atom having atleast one hydrogen atom attached thereto attached to and adjacent to thecarbonyl carbon atom are most effective and comprise a particularembodiment. Accordingly, a particularly preferred group of ketonescomprises the lower boiling ketones; e.g., boiling below about 200 C.,especially acetone, acetophenone, methyl ethyl ketone, and methyl propylketone. It is to be understood that mixtures of the above-describedsolvents can be employed if desired.

The processing techniques of the invention are subject to manyvariations, provided that all three of the main ingredients are broughtinto contact with each other and essentially instantaneously brought tothe desired polymerization temperature. By way of example, separatestreams of the olefinic compound, maleic compound, and catalyst (in eachinstance, with or without the solvent) at temperatures at whichcopolymerization would not take place are brought into intimate contactwith each other in a zone which is maintained at the polymerizationtemperature. This zone is most effectively obtained by using a heel orsink of the aforedescribed solvents maintained at the desiredpolymerization temperature. Thus, in this fashion, incremental amountsof the reagents are essentially instantaneously brought to thepolymerization temperature and reacted essentially instantaneously,whereby there is no build up of unreacted monomers in the reaction zone.The rate of feed of the reagents to the reaction zone is preferablycontrolled so that no more than 3 percent by weight of unreacted monomeris present therein, and more preferably no more than 1 percent by weightof unreacted monomer, at the polymerization temperature. A particularlyeffective processing technique which comprises an especially preferredembodiment of the invention is to employ a completely miscible andhomogeneous solution of the monomers and catalyst which is retained at atemperature below that at which significant polymerization would takeplace as a feed stream to a reactor or reaction zone in which a heel ofthe solvent, preferably the same as the solvent employed in formulatingthe feed solution, is maintained at the desired polymerizationtemperature, generally above about 80 C. By this particular processing,an essentially instantaneous polymerization is obtained whereby nosubstantial build up of unreacted monomer results and there is nouncontrollable reaction to result in the explosive mixtures experiencedheretofore by the prior art processes. Indeed, the polymers so producedhave the unique characteristic of a more narrow molecular weight rangethan obtainable heretofore as exhibited by the fact that, generally, therecovered polymer will have a narrow melting point range. Further, moreselective production of a desired polymer having specificcharacteristics of molecular weight, viscosity, melting point, and molarratio of comonomers in the product is now possible.

The instant invention will be more readily understood from the followingexamples.

EXAMPLE 1 Into a 3-gallon mixing vessel was added 1130 grams of methylethyl ketone. Then there was added thereto, with agitation, 777 grams ofmaleic anhydride. Next 828 grams of styrene and 95 grams of benzoylperoxide were added with mild agitation to effect solution of all of theingredients in the methyl ethyl ketone. All of the mixing operationswere performed at essentially room temperature. The solution so formedis hereafter referred to generally as Solution-A. Into a separateS-gallon stainless steel reaction vessel equipped with internalagitation, a means for externally heating the reactor and its contents,a means for feeding reagents, and a means for discharging the reactionproducts was added 3220 grams of methyl ethyl ketone. This heel ofmethyl ethyl ketone was heated to a temperature of about C. atautogenous pressure (about 65 p.s.i.). Then the Solution-A pre-mixed asdescribed above was continuously fed to the reactor containing the heelover a period of one hour, while maintaining the temperature of thecontents of the reactor essentially constant at about 145 C. by heatingor cooling as required with the pressure at about 65 psi. The reactionwas essentially instantaneous. At the completion of feeding theSolution-A to the reactor, the pressure on the reaction vessel wasreleased causing much of the solvent to vaporize and the reactionmixture (a homogeneous solution) was then subjected to a vacuum in orderto draw off the remaining methyl ethyl ketone. The resultant poly mer,still containing a minor amount of methyl ethyl ketone, was thentransferred to a dryer and dried at 110 C., recovering the methyl ethylketone evolved. The product was pulverized to a white, free-flowingpowder, a sample of which was analyzed. It was found that the productobtained had a melting point range of -160 C. Ten grams of the productthus obtained were dissolved in acetone to a volume of 100 milliliters.The viscosity of this solution was obtained by the standard techniqueemploying an Oswald viscosimeter at 30 C. It was found to have aviscosity of 0.716 centistoke at 30 C. The Gardner color of thissolution was 1.

EXAMPLE 2 The procedure of Example 1 was repeated essentially asdescribed, with exception that in forming the Solution A, 3597 grams ofmethyl ethyl ketone, 1656 grams of styrene, 777 grams of maleicanhydride, and 76 grams of benzoyl peroxide were employed with all otherconditions and proportions being essentially the same. Thus, in thisrun, molar proportions of essentially 2:1 of styrene to maleic anhydridewere employed, and a smaller amount of the benzoyl peroxide wasemployed. When recovering the product and analyzing essentially asdescribed in Example 1, it was found that an essentially 100 percentconversion of all of the reagents to copolymer was obtained,demonstrated that a copolymer of 2 moles of styrene per mole of maleicanhydride was produced. The product had an acid number of 383, whereasthe theoretical is 366; a melting point range of ISO-170 C., with theviscosity of the 10-gram solution thereof in 100 milliliters of acetoneat 30 C. being 0.847 centistoke. The Gardner color of the acetonesolution was 1.

EXAMPLE 3 The procedure of Example 1 was repeated essentially asdescribed, with exception that the Solution-A was formed by dissolving76 grams of benzoyl peroxide, 2484 grams of styrene, and 777 grams ofmaleic anhydride in 3597 grams of methyl ethyl ketone at roomtemperature; and the heel of methyl ethyl ketone present in the reactorwas 3220 grams. Thus essentially 3 moles of styrene per mole of maleicanhydride were employed. Upon recovering the product as described inExample 1, in analysis it was found that the product had a melting pointrange of 170 C. and an acid number of 291. The viscosity in the 10percent acetone solutionwas 0.993 centistoke and the Gardner color was1.

EXAMPLE 4 Solution-A comprising 657 grams of acetone, 123 grams ofmaleic anhydride, 131 grams of styrene, and 5 grams of 30 percentaqueous hydrogen peroxide was slowly added to a 2-liter resin kettlecontaining 590 grams of refluxing acetone. Refluxing of the acetone andstirring was maintained throughout the addition time, which Was 60minutes. The mixture was further stirred and refluxed for an additional30 minutes. The acetone was then distilled off from the mixture, leaving250 grams of essentially dry powder product, representing a yield of98.5 percent. To the product was added 462 grams of water and 302 gramsof a 58 percent ammonium hydroxide solution. The mixture was heated withagitation at 90 C. for two and one-half hours. At the end of this perioda clear solution was obtained of the hydrolyzed resin.

EXAMPLE At room temperature a Solution-A was formed of 285 grams ofmethyl ethyl ketone, 123 grams of maleic anhydride, 131 grams ofstyrene, and 1.5 grams of benzoyl peroxide. In a separate kettle 254grams of methyl ethyl ketone were heated to the reflux temperature; andthen the afore-mentioned reagent Solution-A was fed to the kettle over aperiod of 30 minutes with continuous agitation. The mixture was refluxedfor an additional 30 minutes. Then a vacuum was drawn on the reactor toremove part of the methyl ethyl ketone solvent, leaving a viscous mass(about 429 grams). This mass was transferred to a tray and dried in anoven at 110 C. for one hour. The resulting dried material was brokeninto pieces in a mortar and then dried at 110 C. for an additional onehour. Analysis of the product indicated an acid number of 520, andmelting point range of 225-285 C. The yield obtained was 243 grams, or95.5 percent. When dissolving grams of the product in acetone, dilutingthe solution to 100 milliliters, then determining the viscosity at 30 C.in an Oswald viscosimeter, it was found that the viscosity was 11.9centistokes. Determining the color of the acetone solution according tothe Gardner scale, the color was found to be less than 1.

EXAMPLE 6 The procedure of Example 5 was repeated essentially asdescribed with exception that only 0.03 gram of benzoyl peroxide wasemployed, but all other proportions and materials were identical. Inthis instance 236 grams of dried product were obtained, representing ayield of 93 percent. The product had an acid number of 517, an acetonesolution viscosity of 111 centistokes, and a Gardner color of less than1.

The following example serves to illustrate the production of a 1:1styrene-maleic anhydride copolymer of low viscosity and low molecularweight on a larger scale.

EXAMPLE 7 In this instance, to an 80-gallon stainless steel reactorequipped with external heating and a means for overflow of productsolution at about the 65-gallon level was added 55 gallons of methylethyl ketone. This solvent was heated to 141 C. at a pressure of 70 psi.and maintained at these conditions throughout the run with continuousagitation. In a separate mixing vessel 522 pounds methyl ethyl ketone,100 pounds maleic anhydride, 107 pounds styrene, and 12 pounds benzoylperoxide were thoroughly mixed at room temperature to obtain ahomogeneous solution. This Solution-A was continuously fed to thereactor containing the refluxing methyl ethyl ketone over a period of 4hours with product solution continuously overflowing from the reactor.The overflow stream was collected in an external pressure vessel. Whenthe feed had been completed, thus also stopping the overflow, the

pressure was released from the external collecting vessel, a vacuumdrawn and heat applied to maintain a temperature of 1850 C. to removethe methyl ethyl ketone from the product leaving a melt of the productin the kettle. The product was removed from the kettle by gravity flow,then cooled. The product can be then ground to a freeflowing whitepowder. The product obtained had an acetone solution viscosity at 30 C.of 0.749 centistoke.

The above examples have been presented by way of illustration, and it isnot intended to be limited thereby. Thus, similar results are obtainedwhen other olefinic compounds, maleic compounds, catalysts, solvents,and conditions as described herein are substituted.

The catalysts which are employed according to the process are subject toconsiderable choice among those of the free-radical generating type. Theorganic peroxides or hydrogen peroxide have been found to be mosteffective and thus are particularly well suited to the processing of thepresent invention. Such organic peroxides are illustrated by the variousaliphatic, cycloaliphatic, and aromatic peroxides, particularly thosewhich are preferably soluble in the reaction system and comparativelystable at temperatures below about 60 C. Thus, included among suchorganic peroxides are, for example, tertiary butyl hydroperoxide, cumenehydroperoxide, cyclohexanone peroxide, methyl ethyl ketone peroxide,methyl isobutyl ketone peroxide, acetyl peroxide, benzoyl peroxide,naphthoyl peroxide, lauroyl peroxide, ditertiary butyl peroxide,diacetyl peroxide, dicumyl peroxide, as well as other freeradicalgenerating catalysts such as azodiisobutyronitrile and the like. Thepreferred free-radical generating catalysts are the organic peroxideswhich are comparatively stable up to temperatures of about 60 (1.,especially benzoyl peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-di(t-'butyl peroxy)hexane. Benzoyl peroxide is particularly effective atpolymerization temperatures between about l15 C.; dicumyl peroxide isparticularly effective at temperatures between about to 200 C.; and2,5-dimethyl-2,5-di(t-butyl peroxy)hexane is especially effective attemperatures between about ZOO-250 C.

The proportion of the reagents, solvent and catalyst employed in thecopolymerizations can be varied to a considerable extent, dependingprimarily upon the desired copolymer. For example, by the presentprocessing proportions of olefinic compound to maleic compound, betweenabout 1:1 to 20:1 and higher can be employed to result in polymerscontaining the same molar proportions. It is preferred, however, toemploy molar proportions of the olefinic compound to the maleic compoundbetween about 1:1 to 3:1 respectively. Ordinarily the solvent isemployed in forming the Solution-A in amount sufficient to provide ahomogeneous solution at temperatures below which significantpolymerization Would take place. Further, in the Solution-A of themonomers and catalyst, the concentration of the monomers can varybetween about 5 to 75 percent by weight, based upon the total weight ofthe monomers and the solvent. It is preferred, however, to employconcentrations between about 30 to 60 percent by weight. Likewise, theamount of heel in relation to the Solution-A can also be 'varied butgenerally will range from about 0.25:1 to 110.25 respectively by volume.In preferred embodiments, essentially 1.5 volumes of the Solution-A to1.0 volume of heel are employed, at least for start-up purposes. Ofcourse, in continuous processing, the volume relationship of theSolution-A to the heel solution is of no particular consequence.

The catalyst is also employed in varying proportions, depending uponwhich one is employed, the reaction temperature, and the molecularweight of the copolymer desired. In general, however, catalystproportions of up to about 10 percent by weight, based upon the totalweight of the monomers, are all that are required even though largeramounts could be employed. In preferred embodiments, catalystconcentrations between 0.001 to 5.0 (more especially 0.02 to 5) percentby weight, based on the total weight of the monomers, are employed.

The temperature at which the heel is maintained, i.e., the temperatureof polymerization, can be varied considerably from that temperaturenecessary to initiate reaction up to and including about 300 C. andhigher. In all embodiments, however, it is more practical to employtemperatures between about 75-250 C., preferably l50250 C., with, ifnecessary, autogenous or appropriate pressure conditions by the additionof an inert gas such as nitrogen to maintain the reaction system in theliquid state.

As illustrated by the above discussion and the examples presentedherein, the polymer product is affected, particularly with regard to itsviscosity and molecular weight, by a combination of factors; viz., theconcentration of the monomers in the Solution-A, the temperature ofpolymerization, the concentration of catalyst employed, and the relativeconcentrations of the solvent that is employed. However, the processingis especially effective toward the production of copolymers ofmono-olefinic compound and maleic compound, especially styrene andmaleic anhydride, in molar proportions between about 3 :1 to 1:1,respectively, having melting points below about 225 C., a melting pointrange of less than 25 C., and a molecular weight below 3000 (especiallybelow about 2000), and acetone solution viscosities of less than 1.0centistoke.

While polymerization generally occurs quite readily at temperatures ofthe order of about 75 C. and higher, with certain catalysts it issometimes desirable to employ catalyst activators in order to effectfree-radical initiation at lower temperatures. Among the criterial ofchoice of the catalyst activators is that it be preferably inert to themonomers and solvent at the conditions of polymerization. For thispurpose the amines, especially the dialkyl aromatic amines, are quiteefiective. Another class of activators which can be employed are thecobalt salts as, for example, cobalt hexoate, laureate, palmitate, andnaphthenate, and other cobalt, vanadium, manganese and similar dryingoil fatty acid salts. The amines and cobalt salts comprise the catalystactivators which have been found most effective, although others can beemployed. The dialkyl tertiary aromatic amines wherein the alkyl groupscontain up to about 4 carbon atoms are preferred, especiallyN,N-dimethyl aniline, and the best results are obtained when such areemployed with acyl peroxide catalysts or benzoyl peroxide. The cobaltsalts, especially cobalt naphthenate, are preferred when employingmethyl ethyl ketone peroxide or l-hydroxycyclohexyl hydroperoxide as thecatalyst.

While the proportion of the catalyst activator can be varied, in generalup to about 10 percent by weight thereof, based upon the weight of thefree-radical initiating catalyst employed, has been found practical. Formost efiicient and effective operation, the activator, when employed, isused in amounts between about 0.0001 to about 0.1 percent by weight,based upon the weight of the catalyst.

The following example is illustrative of that embodiment of theinvention wherein the catalyst activators are employed, although it isnot intended to be limited thereby.

EXAMPLE 8 The procedure of Example was repeated essentially asdescribed, with the exception that to the heel of methyl ethyl ketonethere was added 2 milliliters of N,N-dimethyl aniline. At the completionof the reaction and recovery of product, a yield of 98.5 percent wasobtained of resin having an acid number of 534, an acetone solutionviscosity of 2.94 centistokes, and the Gardner color of the acetonesolution was between 1 and 2.

Thus the above example illustrates that the employment of the activatorswill produce a product having a much lower acetone solution viscositythan is obtained when employing the identical conditions in the absenceof the activator. It has been found that, in general, the greater theproportion of the activator in relation to the catalyst, the lower theviscosity of the product obtained. Thus, when the above example wasrepeated substituting 0.15 gram and 0.75 gram of the dimethyl aniline intwo separate runs, acetone solution viscosities of 6.85 centistokes and4.42 centistokes, respectively, were obtained.

Similar results are obtained when other catalyst activators as describedhereinbefore are substituted.

A still further and particularly unique embodiment of the inventioncomprises the replacement of a portion of the a-foredescribed solventsby a different or second solvent which exhibits solubility for themonomers but in which the copolymer produced is normally insoluble. Inthis instance both solvents are employed in amounts which will stillresult in the polymer produced being soluble in the total solvent systemunder the conditions of polymerization. Thus such different or secondsolvents are also soluble in the afore-described solvents, resulting inan essentially homogeneous solution of the product in the reactionsystem. By this processing, many economies are effected in that morecostly solvents can be partially replaced by less costly solvents.Additionally, a more facile recovery of each of the solvents employed inthe mixture of solvents is possible. Still further, it has been quiteunexpectedly found that the mixture of solvents is not deleterious tothe accomplishment of the results desired but, indeed, promotes theformation of a more pure product and is especially adaptable to theformation of the most desired polymers, i.e., those polymers having anacetone solution viscosity below about 1 centistoke and molecular weightbelow 2000, especially of styrene and maleic anhydride. Additionally, ithas been found that the use of mixtures of solvents, especially of aketone and hydrocarbon, results in copolymers having better color andwhose hydrolyzed solutions are less viscous than when a ketone alone isused as the solvent.

Thus, as the cosolvent, conventional hydrocarbons and halogenatedhydrocarbons can be used. Again, these solvents should be liquid underthe reaction conditions and essentially inert, although chain stoppingsolvents can be employed and in most instances are preferred. Includedamong the solvents which can be employed are naphthas and the like andthe aromatics as, for example, benzene, toluene, cumene, p-cymene,xylene, ethylbenzene, tetrahydronaphthalene, and mixtures thereof, andthe like. Among the halogenated hydrocarbons which can be employed areincluded, for example, the various chloro, bromo, and iodohexanes,carbon tetrachloride, methylene dichloride, chlorocyclohexane,chlorobenzene, benzyl chloride, and the like, with the chloro aromaticsbeing most effective.

A particularly unique class of cosolvent to be employed is a hydrocarboncompound of the above type in which a carbon atom is attached to a6-membered carbocyclic ring with at least one hydrogen attached to thecarbon atom, and the remaining valences of the carbon atom are satisfiedby a radical selected from the group consisting of alkyl, aryl, andalkaryl radicals, preferably alkyl in which the alkyl group containsfrom 1 to 4 carbon atoms. The employment of this particularly uniqueclass of cosolvent in conjunction with the principal solvents discussedpreviously enhances the production of copolymers in even greaterselectivity having more desirable molecular weight, melting point, andviscosity characteristics, especially when styrene and maleic anhydrideare employed. Included among the especially preferred solvents of thisparticular type are cumene, o-, m-, or p-cumene, diisopropyl benzene,and triisopropyl benzene.

The following examples will illustrate this embodiment of the invention.

EXAMPLE 9 The procedure of Example 1 was again employed essentially asdescribed therein. In this instance, 1130 grams to and maintained duringthe course of the run at a temperature of about 176 C. with the pressuremaintained at about 97 p.s.i.g. with agitation. The Solution-A was fedto the pre-heated heel continuously over a period of one hour. At thecompletion of the feeding, the pressure was released from the reactorand a vacuum drawn to remove the methyl ethyl ketone. Then furthervacuum was drawn to remove the cumene solvent. The viscous suspension ofpolymer wet with cumene was removed from the reactor and Washed withpetroleum ether. The washed product was then ball-milled with about 3liters of petroleum ether, filtered, and dried at 110 C. The resultantfree-flowing white powder had an acetone solution viscosity of 0.642centistoke and the Gardner color was 1.

EXAMPLE The procedure of Example 9 was repeated essentially asdescribed, with exception that only 38 grams of dicumyl peroxide wereemployed as the catalyst and the heel comprised 4000 milliliters ofequal parts by volume of the cumene and methyl ethyl ketone, with allother conditions being essentially identical. The product which wasrecovered had an acid number of 494, a melting point range of 175l85 C.,with the acetone solution viscosity being 0.682.

EXAMPLE 11 Employing the procedure essentially as described in Example7, the solution-A was prepared employing 471 pounds of solvent mixturecomprising 70 percent by weight cumene and percent by weight methylethyl ketone. With agitation 150 pounds of maleic anhydride, 321 poundsof styrene, and 1110 grams of dicumyl peroxide were added and mixedthoroughly at room temperature. In the reactor there was contained 65gallons of a previous run of a 70/30 mix of cumene and methyl ethylketone and 50 percent polymer by weight. This solvent mix was maintainedat 227 C. at ll50 p.s.i., with these conditions being maintainedthroughout the run. The Solution-A was fed to the pre-heated heel at arate of 3 /2 to 5 /2 pounds per minute of reactants. At the completionof the feed, the product was recovered as described in the precedingexample, This product had an acetone solution viscosity of 0.745, aGardner color of 1, and an essentially quantitative conversion wasobtained of copolymer containing styrene to maleic anhydride in themolar ratio of 2: 1, respectively.

The above examples have been presented by way of illustration of thatembodiment of the invention employing mixed solvents, and it is notintended to be limited thereto. By appropriate substitution,particularly of the ketones and the above-described hydrocarbonsolvents, similar results are obtained.

In the mixed solvent systems illustrated by the preceding examples, itis preferable to employ a cosolvent, especially a hydrocarbon solvent,having a boiling point above that of the other solvent, particularly theketone. In general the cosolvent should have a boiling point at least 20degrees higher than that of the principal solvent. The amount ofcosolvent employed in relation to the amount of principal solvent can bevaried over a considerable range, provided that both the monomers andthe polymer product are essentially completely soluble in the solventmix at reaction temperature and pressure. In general, amounts betweenabout 20 to 75 percent by weight of cosolvent, based on the total weightof solvent, are employed; however, for most effective operation, betweenabout to 70- percent by weight of the second or cosolvent based on thetotal weight of solvent are employed.

As briefly indicated hereinabove, the copolymer products producedaccording to the invention are of considerable utility. Thus, they canbe used in adhesives and binders, coatings for paper, ceramic, leather,textiles, and the like. They can also be employed in the preparation ofaqueous solutions with alkali metal, ammonium, or

organic bases, particularly the low molecular weight, low viscositycopolymers which result in solutions, in water, of low viscosity. Thesesolutions are quite adaptable in coating applications. Still further,the solutions of copolymer as directly obtained from the reaction can beemployed in coating applications. Additionally, the copolymer productscan be reacted with monohydric alcohols to form various esterificationproducts, including partial esters, half esters, and full esters, whichare also useful in coating compositions. Additionally, the products canbe cross-linked with various polyhydric alcohols to produce compositionsreadily susceptible to coating operations. Still other uses for theproducts produced will now be evident.

Having thus described the process of this invention, it is not intendedto be limited except as set forth in the following claims.

I claim:

1. A process for the manufacture of copolymer which comprisessimultaneously bringing a compound having a terminal polymerizablecarbon-to-carbon double bond, a maleic compound having the structuralformula:

&

wherein R and R are selected from the group consisting of hydrogen,halogen, sulfonic acid, alkyl, aryl and aralkyl radicals and X and Y areselected from the group consisting of hydroxy, alkoxy, aryloxy andhalogen radicals or X and Y are both supplied by a single 0 or NHradical, and free-radical initiating catalyst into contact with asolvent which has been pro-heated to a polymerization temperature ofabout to 300 C., and which is a solvent for both the monomers and thecopolymer produced.

2. A process for the manufacture of a styrene-maleic anhydride copolymerwhich comprises feeding a solution of styrene, maleic anhydride, andfree-radical initiating catalyst in methyl ethyl ketone to a pre-heatedheel of methyl ethyl ketone which is maintained at a polymerizationtemperature of about 75 to 300 C. and contains less than about 3 percentby weight of unreacted monomer therein.

3. The process of claim 2 wherein said methyl ethyl ketone heel ismaintained at a temperature between about l50250 C.

4. The process of claim 3 further characterized in that said maleicanhydride and styrene are employed in essentially equimolar quantities,said catalyst is benzoyl peroxide and is employed in amount betweenabout 0.02 to 5 percent by weight, based upon the total weight ofmonomers, said solution contains approximately 50 percent by weight ofsaid monomers and catalysts, based upon the total weight of saidsolution, and said heel comprises approximately an equal volume to thatof said solution.

5. The process of claim 3 wherein said styrene and maleic anhydride areemployed in molar proportions of at least 2 to 1 respectively.

6. A process for the manufacture of a copolymer which comprisessimultaneously bringing a compound having a terminal polymerizablecarbon-to-carbon double bond, a maleic compound having the structuralformula:

wherein R and R are selected from the group consisting of hydrogen,halogen, sulfonic acid, alkyl, aryl and aralkyl radicals and X and Y areselected from the group consisting of hydroxy, alkoxy, aryloxy andhalogen radicals or X and Y are both supplied by a single or NH radical,and a free-radical initiating catalyst into contact with a mixture of atleast two different solvents which has been pre-heated to apolymerization temperature of about 75 to 300 C., and in which one ofsaid solvents is a solvent for both the monomers and the copolymerproduced, and the other solvent is a solvent in which the monomers aresoluble but the copolymer produced is normally insoluble, said copolymerbeing soluble in the reaction mixture.

7. The process of claim 6 further defined wherein one of said solventsis a ketone and the other solvent is an aromatic hydrocarbon.

8. The process of claim 7 further defined in that said mixture ofsolvents is maintained at a temperature between ISO-250 C.

9. A process for the manufacture of a styrene-maleic anhydride copolymerwhich comprises feeding a solution of styrene, maleic anhydride, andfree-radical initiating catalyst dissolved in a mixture of methyl ethylketone and cumene to a pre-heated heel of a mixture of methyl ethylketone and cumene which is maintained at a temperature between aboutISO-250 C. and contains less than about 3 percent by weight of unreactedmonomer therein, said copolymer being soluble in the reaction mixture.

10. The process of claim 9 further characterized in that said maleicanhydride and styrene are employed in essentially equimolar quantities,said catalyst is benzoyl peroxide and is employed in amount betweenabout 0.02 to 5 percent by weight, based upon the total weight of themonomers, said solution contains approximately percent by weight of saidmonomers and catalyst, based upon the total weight of said solution,said heel comprises approximately an equal volume of said solution, andboth said solution and said heel comprise approximately equal parts byweight of said methyl ethyl ketone and said cumene.

1. The process of claim 9 wherein said styrene and maleic anhydride areemployed in molar proportions of at least 2 to 1 respectively.

References Cited UNITED STATES PATENTS 3,207,718 9/1965 Zimmerman et al.26078.5 2,744,098 5/1956 Towne 260-78.5 2,294,226 8/ 1942 DAlelio260--32 2,606,891 8/1952 Rowland 260-785 2,675,370 4/1954 Barrett26078.5 3,336,267 8/1967 Zimmerman et al. 260-78.5

OTHER REFERENCES Websters New International Dictionary (1954).

JOSEPH SCHOFER, Primary Examiner.

I. KIGHT, Assistant Examiner.

U.S. Cl. X.R. 260

